180 MOBPHOLOGY AND EVOLUTION
and scalenus posticus. It breaks up into slips which are inserted into the posterior tubercle of the atlas and the occipital bone below the crest. On the atlas its insertion is fused with the levator scapulae and omo-trachelian. In other Apes there are also individual variations in the characters of the sacro-spinalis.
The complexus (fig. 34) in the Gorilla is divisible into complexus and biventer cervicis as in Man. In three Chimpanzees I found no trace of this division; the muscle formed close parallel slips running from the articular processes of the lower five cervical and upper six dorsal vertebrae to the occipital crest. In these animals the semispinalis dorsi, semispinalis colli and multifidus spinae were very similar to those in Man.
The sub-occipital triangle is small or quite obliterated by the approximation of the bounding muscles. The obliquussuperior(fig. 34, B) (S.O.jVL), obliquusinferior (I.O.M.), and rectus capitis lateralis are as in Man. The rectus capitis posticus major (E.G.P.M.) is a powerful pyramidal muscle running from the spine of the axis to the occipital bone beneath the entire length of the superior oblique. It conceals the rectus capitis posticus minor, which runs from the inner three-quarters of an inch of the posterior arch of the atlas to the occipital bone beneath the major muscle. The interspinales, intertransverse, rotatores and levatores costarum are well marked.
Prevertebral Muscles.—In the Chimpanzee the longus colli consists of vertical, superior and inferior parts as in Man. The vertical part runs from the bodies of the lower two cervical and upper four dorsal vertebrse to the bodies of the second, third and fourth cervical